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Questions and Answers
What are enzymes primarily classified as?
What are enzymes primarily classified as?
Enzymes change the reaction equilibrium.
Enzymes change the reaction equilibrium.
False
Name one of the fastest known enzymes.
Name one of the fastest known enzymes.
Carbonic anhydrase
Enzymes are __________ that increase the reaction rate.
Enzymes are __________ that increase the reaction rate.
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Which of the following is NOT one of the enzyme classifications?
Which of the following is NOT one of the enzyme classifications?
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Match the following enzyme classifications with their descriptions:
Match the following enzyme classifications with their descriptions:
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Enzymes can be consumed during the reaction they catalyze.
Enzymes can be consumed during the reaction they catalyze.
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What factor does enzyme activity directly relate to when discussing reaction rates?
What factor does enzyme activity directly relate to when discussing reaction rates?
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Which part of the enzyme is referred to as the Apoenzyme?
Which part of the enzyme is referred to as the Apoenzyme?
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The activity of an enzyme is measured by the amount of substrate converted to product in a given time.
The activity of an enzyme is measured by the amount of substrate converted to product in a given time.
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What are the two types of inhibitors that can affect enzyme activity?
What are the two types of inhibitors that can affect enzyme activity?
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The catalytically active form of an enzyme is known as the ______.
The catalytically active form of an enzyme is known as the ______.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Which of the following factors does NOT affect enzyme activity?
Which of the following factors does NOT affect enzyme activity?
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Enzymes only function at a single specific temperature and pH.
Enzymes only function at a single specific temperature and pH.
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What is the unit of enzyme activity defined as?
What is the unit of enzyme activity defined as?
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Study Notes
Enzymes
- Enzymes are biocatalysts that speed up reactions.
- They have common properties like being proteins (except for ribozymes which are RNA).
- Enzymes lower activation energy, thus speeding up reactions.
- Enzymes are not consumed or changed in the reactions.
Learning Objectives
- Describe enzymes and their properties
- List enzyme classifications in correct order
- Describe factors that change enzyme activity
- Explain the relationship between Km and activity
- Explain enzyme inhibition and inhibition types
Metabolic Reactions
- Enzymes facilitate metabolic reactions.
- They accelerate both anabolic (build-up) and catabolic (breakdown) reactions.
- Enzymes modify molecules, degrade molecules, bind molecules together and transport molecules.
- Enzymes operate with some special molecules.
Glycolysis
- Glycolysis is a metabolic pathway.
- Enzymes are shown working in glycolysis.
Metabolism of Complex Carbohydrates and more
- A complex diagram shows how the metabolism of different molecules are interrelated.
Activation Energy
- Activation energy is needed to start a reaction.
- Enzymes lower the amount of activation energy needed.
Activation Energy and Catalysts
- Catalysts increase reaction rates by decreasing activation energy.
- Enzymes are catalysts.
Enzymes (Biocatalysts)
- Enzymes are biocatalysts.
- Enzymes increase reaction rate.
- They act on substrates (reactants).
Properties of Enzymes
- Most enzymes are proteins.
- Ribozymes are catalytic RNA.
- Enzymes change reaction rate (efficiency), not equilibrium.
- They have specificity for substrate and reaction.
- Enzymes have substrate and reaction specificity, which makes them efficient.
Efficiency
- Enzyme-catalyzed reactions are very efficient compared to uncatalyzed reactions (10^3 - 10^8 times faster).
- Carbonic anhydrase is a fast enzyme.
Specificity
- Reaction Specificity: One enzyme catalyzes one specific reaction type.
- Substrate Specificity: One enzyme acts on one specific molecule or chemically related molecules.
Enzyme Nomenclature: Classification
- Enzymes are classified into groups based on their function.
- The classification uses an EC number.
- The groups are Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases, and Translocases.
Table of Contents
- The enzyme database is organized by class, subclass, and sub-subclass.
Enzyme Structure
- Apoenzyme: protein part of an enzyme.
- Cofactor: non-protein part of an enzyme.
- Holoenzyme: catalytically active enzyme.
- Active Site: region that interacts with substrate.
Enzyme Structure: Active Site
- Specific amino acids in the active site interact with the substrate.
Enzyme Activity
- Activity is reaction speed (V).
- Unit activity change; 1 µmol substrate in 1 minute, under optimal conditions.
Factors Affecting Enzyme Activity
- Enzyme concentration, substrate concentration, temperature, pH, and inhibitors affect enzyme activity.
- Temperature, pH, and inhibitors can change the enzyme's shape and how it functions.
Enzyme Concentration
- Higher concentrations of enzymes results in faster reaction rates.
Substrate Concentration
- Increasing substrate concentration increases reaction rates up to a point, where the enzymes are working at their maximum speed.
- Km is the substrate concentration where the reaction rate is half its maximum value (Vmax).
Temperature
- Temperature affects the reaction rate.
- Enzymes have optimum temperatures and are inactivated at high temperatures.
pH
- pH affects the reaction rate.
- Enzymes have optimum pH values, outside of which the enzyme activity decreases.
Inhibitors
- Inhibitors decrease the velocity of an enzyme-catalyzed reaction.
- Competitive inhibitors bind to the active site.
- Noncompetitive inhibitors bind to a different site.
- Some inhibitors are reversible, some are irreversible.
Reversible Inhibition
- Reversible inhibitors can bind or unbind from the enzyme.
- Competitive inhibitors: compete with substrate for binding to active site and prevent product formation.
- Non-competitive interactions: bind at a different location and prevent product formation.
Enzyme Kinetics and Km
- Km reflects the enzyme's affinity for the substrate.
- A lower Km means higher affinity.
Km, A Clinical Example
- Km values are used in clinical settings to understand how a substance interferes with the function of enzymes.
- Alcohol dehydrogenase changes ethanol to acetic acid in the body.
Regulation of Enzyme Activity
- Enzyme activity can be regulated by changes in enzyme amount, enzyme modification, and compartments.
- Enzymes are regulated by synthesis, degradation, covalent modifications, and compartmentalization.
- The activity will regulate reaction rate.
- Feed-back loop (inhibition).
- Feed-forward activation.
- Enzymes can be in different compartments of the cell.
Regulation of Enzyme Activity
- Phosphorylation and dephosphorylation are covalent modifications that regulate enzyme activity.
Regulation of Enzyme Activity
- Specific compartments or locales of cells regulate enzymes.
Regulation of Enzyme Activity
- Isozymes are enzymes with identical catalytic activity but different composition & structure.
- Isozymes can be in different locations (compartments).
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Description
This quiz explores the fascinating world of enzymes and their role in metabolic reactions. You will learn about the properties of enzymes, enzyme classifications, and the factors affecting their activity. Dive into the specifics of glycolysis and understand how enzymes facilitate various metabolic pathways.
